Treatment of drilling fluids



Patented Jan. 15, 1946 TREATMENT OF DRILLHVG 'FLS Raymond W. Hoeppel, Arcadia, ilalifi, assignor to National Lead Company, Los Angeles, Calli a corporation of New .lersey No Drawing. Application April 7, 1943, Serial No. 482,210

18 Claims.

This invention relates to the art of chemically treating drilling fluids, such as are used in the ,increase the hydrostatic head, and frequently containing also concentrated colloidal suspending and conditioning agents such as bentonite.

The drilling fluid serves to bring cuttings to the surface, to cool the bit. and to keep oil, gas and water confined to their respective formations during the drilling process. For these functions it is necessary that the drilling fluid be of pumpable viscosity, have sumcient gel-strength to bring cuttings to the surface, and yet be fluid enough to release cuttings and entrained gas at the surface.

A highly important property of drilling muds is the ability to form an impervious filter cake upon the permeable walls of the-bore hole, thus inhibiting further ingress of water from the drilling fluid into the formation. A drilling mud deficient in this property allows an undue amount of water to enter the formation, which leads to caving and loss of production in productive formations, and also permits the ftlon of a thick filter cake which may stick the drill stem. and in any case greatly increases the swabblng action when the bit is withdrawn from the hole.

In the drilling of a well, formations are encountered, the cuttings of which will enter the fluid and may contaminate the same with hydroxyl ions. These disadvantageously affect the viscosity, gel strength and water loss of the fluid. For example, less than 1% of calcium hydroxide, may serve to cause an otherwise freely flowing drilling fluid to change into a plastic mass even thicker than commercial mayonnaise, so that the fluid is thereafter not pumpable, fails to deposit cuttings in the ditch, becomes gas-cut, i. e., retains gas picked up in the hole so that its effect of density becomes lighter and lighter, making pumping even more dlfllcult, and completely loses its useful walling properties.

In well drilling it is frequently necessary to seal on formations by cementing; thereafter, the drilling is frequently proceeded with after such cementing. As is well known, hydraulic cement even after it has set contains a great deal of free lime, and thus is capable of adding calcium ions to water in contact therewith, not only because of this free lime content, but probably also because of its content of semi-soluble calcium alumino silicates and other calcium compounds.

One of the objects of this invention, therefore,

' is to provide means of treating such contaminated drilling fluids to counteract or inhibit their contamination by hydroxyl ions.

Another object is to provide a process for such treatment.

Another object is to provide a drilling fluid and composition which will counteract or inhibit contamination of the fluid by hydroxyl ions.

Further objects will appear from the detailed description in which will be set forth a number of embodiments of this invention; it will, however, be understood that this invention is susceptible of various embodiments within the scope of the appended claims.

Generally stated, and in accordance with this invention, where the drilling fluid is subject to substantial contamination by hydroxyl ions or is so contaminated, there is employed a salt of an acid whose calcium salt is insoluble, and of a base whose sulfate salt is insoluble and which itself is sufficiently soluble to react with sulfates, together with sulfuric acid or a soluble sulfate of a metal whose hydroxide is insoluble. A particular clam of the first named salts are those of a group conslstlng or most barium and strontium salts of carbonic, orthophosphorlc, oualic and tartaric acids; the second named reagents are of a. group consisting of sulphuric acid and its sodium, p0- tasslum or ammonium salts or the sulfates of those basic elements whose hydroindes are insoluble in the fluid. The reagents are sufliciently soluble to react with each other and cause one of their reaction products to react with and cause conversion of the hydroxyl to water or to a precipitate, but without leaving any undesirable ions in he drilling fluid. Sufficient of the second named reagent is employed to produce a substantial reaction product for conversion of the hydroxyl.

A particular effective means and method is by the employment of barium carbonate and ferric sulfate. The reactions reference calcium hydroxlde are as follows:

3BaCOa +Fe2(SO4) 3B8.SO4+Fe2 (C03) 3 Fez(COz) a+3Ca(OH) z 2Pe(OH) a+3CaCOa From the above it will be seen that the final products'are precipitates and insoluble in the drilling fluid and all are inert. Barium sulfate and barium-carbonate are both mud weighting The amount of the counteracting or inhibiting compounds required will depend upon the nature and proportion of the hydroxyl ions which have and barium tartrate. Strontium salts, such as strontium oxalate and strontium tartratemay also be employed'instead of barium carbonate.

All of these are generally insoluble but are sufriciently soluble in drilling fluids to react with ferric sulfate.

Instead of ferric sulfate there may also be employed the copper, magnesium, nickel, acid sodium or ammonium salts of sulfuric acid, such as copper sulfate, nickel sulfate, acid sodium sulfate (rial-I804) and the aonium sulfates (NH4HSO4 or (0118011). Ferrous sulfate (M501, 71-120) may also be employed. Sulfuric acid may also be used, in which case the reactions are as follows:

it will again be seen thatthe precipitates, barium sulfate and calcium carbonate are insoluble in water, while the remaining reaction product is water.

3 Generally stated, the iron cation is superior to the sodium cation, inasmuch as the iron cation is entirely precipitated from the solution and lowers the pH. The ammonium cation is also or are liable to enter the fluid, for the action is one of counteracting or inhibiting the effect of the hydroxyl ions. Where the compounds are of a nature which are themselves otherwise inert andotherwise produce resulting compounds which are inert, an excess can do no harm and may, in fact, improve the drilling fluid. That is particularly true of the barium and strontium compounds, which themselves are mud weighting materials and result in compounds which are mud weighting materials.

The compounds may be furnished as a part of prepared mixtures, for instance, of barium carbonate and ferric sulfate. The barium and strontium compounds may, moreover, be admixed in a mixture with bentonite or barium sulfate or both. Barium carbonate and ferric sulfate may. moreover, be admixed with barium sulfate or bentonite or both. Moreover, a mud thinner,

. such as caustic and quebracho extract, or disodium dihydrogen pyrophosphate may be incorporated in any of the above mixtures.

In order to illustrate the practical applications of this invention, the following tests and results will be given:

A drilling mud which, when added to water, contained 38% solids at 18 centipoises and also superior to the sodium cation, as it is a weaker 0.8% of bentonite was contaminated with 2 base, and as eventually it is removed by volatilit per barrel oi cement and treated with zation with a subsequent lowering of 1 when the following results:

Initial After 18 hours at 155 F.

No. Thinner Added type {25$ Vise. pH 3; Vise. pH Inl. gel rm. gel 2;

Lb./bbl. Minutes Cmtlpoiees Millimerc Centlpolus Grams Grams Mlllllltera (1).... 0 Blank E110 cement).. 18.2 8.70 19.0 8. 70 MM) 2).--. 0 Blank 11.31 11.32 35.8 3).- 0.70 NaHC 242 11.32 22.5 35.2 11.18 25.0 (4). 1.40 NaHCOa 10.0. 10.40 17.9 11.2 11.00 7 as 10.0 (a)- 53 3 1610 0.28 12.2 9.62 10 to 20.2 (s) g; gg gg 17.8 am 1110 9.13 17 as 20.4

Plastic.

that is desired. It will be noted with reference to sulfuric acid that while it is added to the fluid it is immediately converted by the barium carbonate, particularly where, as is preferable, the barium carbonate is added to the fluid before the addition of the suliuric acid or the other suliate reagents enumerated above.

The counteracting or inhibiting compounds 7 may be employed in any suitable mannenas by adding them to the drillingfluid to become mixed termined, for example, with cement by adding the compounds before the drill reaches the formation containing the cement, whose depth is already known. In this way the fluid will be maintained in its previously prepared. condition. or even improved, and less or the compound will be required.

In these tests the viscosity is in centipoises (cpe.) StOrmer, the pH is in accordance with the Beckman pH meter, the gel strength is in grams (3.) with the initial gel strength immediately:

after agitation and-the final gel strength after 10 minutes, and the water loss is in milliliters (ml.) taken after 30 minutes (30'); all of these are in accordance with standard practice.

Test (2) shows that the fluid has become plastic (P1) that the pH has taken a sharp rise, and that the water loss has almost doubled. Tests (3) and (4) show treatments with a commercial treating agent, namely, sodium bicarbonate. Tests (9) and (10) show treatments in accordance with this invention. The following will be observed: the visooslties in tests (3)-(6) have been restored in all cases. In tests (5) and (6) the pH has been reduced a greater extent than even in (4) However, the greatest improvement in (5) and (6) takes place after heating the fluid, while the viscosities in (4), (5) and (8) are comparable again. The pH in (5) and (6) has 1 See Drilling Mud May 1940 pp. 4 etc. deccrihin the zlaoavee aro cidure, or see 'American Petroleum Instltute ascarcc not risen materially and has remained below that of (3) and (4).; The water losses are, moreover, about the same for (4), (5) and (6). However, an improvement of (5) and (6) is shown in the gel strength, which is substantially lower than that of 4 and is definitely improved.

A test was made on a Mojave mud (known as P-34), which when made up into a fluid of 18' centipolses contained 40% solids. This after being "cement cut" with 2 pounds per barrel of cement and treated with sodium bicarbonate and the compounds in accordance with this tion, showed the following results:

invengypsum contamination: and the barium carbo- No Thinner Added type 52% Visa. pH Vise. 1m. gel rm. gel pH ay LbJbbl. Minutes Centipolsu aromas" cmi oaa Grams crate Malawi 1 Blank (no cement)-- we can as no 8.6 2) 0 Blank 871th 0911161117) 45 12. 06 l2. 1O 14. 2 3)..-- 1. l2 NBHC l 1 5 21.8 10. 76

g ..bd8 5 21. 8 10. 62 10. 8 21. 0 10 110 ll. 75 10. 4 8 a. (6) t #33 $5 10 aao aoo a 1'68 FMBO), 23.8 9.72 10.4 18.7 5 55 10.69 11.0

Here again the treatment, in accordance with this invention, shows not only a greater reduction in pH, but also in gel strength within a better operable range, while the water losses are about the same and the vlscoslties are within a good range.

Not only does this invention effect the counteracting and inhibiting action of contamination by calcium and hydroxyl ions, such as in cement, but one of the two compounds is also effective in itself in counteracting or inhibiting sulfate ions. For example, where barium carbonate is used as one of the pair of treating agents, then in the event that gypsum is encountered, the action is as follows:

BaCOa+CaSOs- BaSQ4+CaCOz It will be seen that again the sulfate is precipitated as barium sulfate, and that the latter, as well as calcium carbonate, are weighting materials. In this case it is only necessary to employ sumcient barium carbonate to satisfy the calcium sulfate, as well as the ferric sulfate, in

' order to convert both the sulfates into barium sulfate. However, an excess of barium carbonate will do no harm but indeed improve the fluid, because of its mud weighting properties. In accordance with this invention, therefore, the compounds may be employed to counteract and inhibit the effect not only oi cement cut muds, but also of gypsum, and even of sodium sulfate, which similarly is converted to barium sulfate and sodium carbonate. 7

It will, therefore, be seen that the invention accomplishes its objects. A simple means is provided for the elimination of any effect of cement or other hydroxyl ions, and even of the effect of gypsum and other sulfates. All of this is accomplished by materials which are available at low prices; for barium carbonate may be used in its natural state as Witherite, and strontium sulfate, in its natural state, as Strontianite.

Ferric sulfate is, moreover, comparatively cheap.

As compared to the employment of sodium bicarbonate, this invention has the following advantages:

The pH of the mud is reduced to a lower value: the viscosity of the mud is reduced to a lower value; considerably lower final gel strengths result, thus reducing damage from the swabbing effect. The barium carbonate used also removes contamination by hydroxyl ions during the course of drilling. the process comprising, adding to the fluid a salt of an acid whose calcium salt is insoluble and of a base whose sulfate salt is insoluble and which itself is sufllciently soluble to react with sulfates. together with a sulfate of a metal whose hydroxide is insoluble.

2. In the art of drilling wells by the employment of a mud-laden fluid subject to substantial contamination by hydroxyl ions during the course of drilling, the process comprising, adding to the fluid a salt of an acid whose calcium salt is insoluble and of a base whose sulfate salt is insoluble and which itself is sufflciently soluble to react with sulfates, together with a reagent of a group consisting of sulphuric acid and its sodium, potassium and ammonium salts and the sulfates of those basic elements whose hydroxides are insoluble.

3. In the art of drilling wells by the employment of a mud-laden fluid subject to substantial contamination by hydroxyl ions during the course of drilling, the process comprising, adding to the fluid a salt of a group consisting of the barium and strontium salts of carbonic, oxalic, orthophosphoric, and tartaric acids and which salt is sufficiently soluble to react with sulfates, together with a reagent of a group consisting of sulphuric acid and its sodium, potassium and ammonium salts and the sulfates of those basic elements whose hydroxides are insoluble.

4. In the art of drilling wells by the employment of a mud-laden fluid subject to substantial contamination by hydroxyl ions during the course of drilling, the process comprising, adding to the fluid barium carbonate and ferric sulfate.

5. In the art of drilling wells by the employ, ment of a mud-laden fluid subject to substantial contamination by cement, the process comprising, adding to the fluid a salt of a group consisting of the barium and strontium salts of carbonic, oxalic, orthophosphoric and tartaric acids and which salt is sufliciently soluble to react with sulfates, together with a reagent of a group consisting of sulfuric acid and its sodium, potassium and ammonium salts and the sulfates of those basic elements whose hydroxides are insoluble.

6.. In the art of drilling wells by the employment of a mud-laden fluid subject to substantial contamination by cement, the process comprls.

to the eeclocnste one,

ierric emicte.

i. in tile oi clrilluig wells by time employ ment oi o m lcclen suuiect to substantial contamination nyiirosyl ions curing time course the process communism-g, out ine to the of drilling, finial u suit of group consisting of the precipi lasted barium one; strontium salts oi carbonic,

oxalic, orthoplcosphoric terterlc seicis ens-l which suit is sufilciently scluble to react with" sulfates, together with a. reagent oi group con sisting of sulfuric acid its sodium, potassium therefrom, con;

of drilling, the process comprising, coding to the fluid csubstontiel period before such contemino= tion, a salt of on cold whose calcium salt is in soluble and of is loose whose sulfote salt is in soluble and which itseli is suficiently soluble to reset. with suliot&, together with e sulfate oi u metal whose hydrornde is insoluble.

9. In the art of drilling wells by the employ-= merit of n mud lnclen fluid subject'to substantial contamination by cement, the process compris= lug, adding to the fluid a. substantial period be, fore sucn cont e salt of a. group consisting of the barium and strontium salts of corbonic, oxalic, orthophosphoric and tartaric acids and which salt is sciently soluble to react with sulfates, together with s reagent of n group con slsting of sulfuric acid and its sodium, potossium and ammonium salts and the sulfates of those bnsic'elements whose hydroxides are insoluble.

it). In the art of drilling wells by the employment of o mud-laden fluid subject to substantial contamination by hydroxylsnd sulfate ions dun ing the course of drilling, the process comprising, adding to the fluid a. salt of on. acid whose celcium salt is insoluble and oi a. loose whose sulfate salt. is insoluble and which itself is sciently soluble to react with. sulfates, together with o.

sulfate of a metal whose hydroxide is insoluble.

- 11. In the art of drilling wells by the employsulfate.

.12. in the ment oi as mus-loose fl is ing the connect soloing to the iii calcium stilt main. is an, r fete salt is insoluble 3 3 is soluble to react with suliews, tcgetn sufiicient of s; of 3. metal. is insoluble, to .gironuee suns product in? conversion of the we of aqueous to remove l therefrom, comprising, c, salt of e, or on= sitting oi the barium and strontium of oer iconic, oxalic, ortnopncsplierle and tel Josie acids and which suit is suii'leiently soluble to react with sulfates, together with suficient of a. reagent oi as group consisting of sulgrlun'ic eclci and its so= oi, potassium and ammonium salts and tire sulfates of those basic elements whose hydroxides are insoluble, to nroduce 2; substantial reection product for conversion of the hydrozyl, 15. A prepared composition for the treatment oi aqueous l1, 1 fluids to remove liyoz'oxyl ions therefrom, comprising, barium carbonate and scient ferric sulfate to nro-duoe ssubstantial reaction product for conversion of the liydronyl. 16 An nqueom mud-laden well drilling fluid containing a. salt of on acid whose calcium salt is insoluble enol of a. base whose suliete salt is insoluble and which itself is sufficiently soluble "to react witlrsulfetes, together with suf icientof e sulfste of e metal whose hydroxide is insoluble, to produce o substantial reaction product for conversion of the hydroxyl. i

ll". An aqueous mud-laden well drilling fiuicl contoi a. suit of a group consisting of the loorlumunu strontium salts of cnrbonie, oxalic, orthop'n'osnlioric, and tartaric coins and which salt is suficlently soluble to react with sulfates,

. together with sumcient of s reagent of a. group ment of o mud-laden fluid subject to substantial contamination by hydroxyl and sulfate ions during the course of drilling, the process comprising,

adding to the fluid or salt of s group consisting of the barium and strontium salts of carbonic, oxalic, orthophosphoric and tartaric acids and which salt is sufliciently soluble to react with sulfates, together with s reagent of a group con= slsting of sulphuric acid and its soul, notes slum and nonium salts and the sulfates of those basic elements whose hydroxides ere in soluble.

consisting of sulfuric acid and its sodium, potassium one onium salts and the sulfotes oi tiiosebaslc elements whose hydroxides are insoluble, to produce s substantial reaction prool not for conversion of the hyciroxyl.

. is. An aqueous mud-laden well drilling fluid containing barium carbonate and suficlent ferric sulfate to produce n substantial reaction. ioroduct for conversion of the hyzyl.

numeric w. noneenn 

